Cronulla will turn to rookie halves Connor Tracey and Braydon Trindall on Sunday with Shaun Johnson sidelined by injury and Matt Moylan racing the clock to be fit against the Sea Eagles.

Johnson's season at the Sharks is hanging by a thread after the playmaker was ruled out for 4-8 weeks after scan results returned a high-grade hamstring injury.

pan66.com understands Johnson has avoided surgery but will be managed through his rehabilitation in the coming weeks with the best-case scenario being a four-week return.

A longer stint on the sidelines is also not out of the question with a four to eight-week timeframe confirmed by the club.

Moylan has been named on an extended reserves list as he looks to make his way back from a calf injury.

Johnson forced from the field with leg injury

In better news, the Sharks welcome back veteran Aiden Tolman from suspension and Will Chambers following a stint in isolation forced upon him by COVID-19 protocols.

For the opposition, the Sea Eagles have confirmed Sean Keppie will return to Sydney with his wife Laura due to give birth next month.

The forward will be replaced by Karl Lawton on the bench, while Curtis Sironen also makes his long-awaited return from knee and hamstring injuries. 

In other NRL team changes, the Panthers have been rocked by the loss of Origin winger Brian To'o and utility forward Tyrone May with each unlikely to play before the finals.

To'o suffered a syndesmosis injury in the first half against Brisbane and while he was able to play out the game, the club expects him to require surgery and spend around six weeks out.

Penrith winger Brian To'o. ©Grant Trouville/NRL Photos

May suffered a medial ligament injury in his left knee in the opening minutes of the win over the Broncos and will also be sidelined for an extended period, according to the club.

To'o will be replaced by Robert Jennings while Matt Burton will partner Jarome Luai in the halves.

The Bulldogs have recalled Kyle Flanagan for their showdown against the Titans after a month on the sidelines due to mixed form, while Adam Elliott returns from a cheekbone injury.

Newcastle have returning troops of their own with Bradman Best (ankle) and David Klemmer (concussion) named to return.

The Knights have included Mitchell Pearce (hamstring) in the reserves for their must-win clash against the Raiders, who welcome back Jack Wighton and Elliott Whitehead.